Continued support is sought for the study of human and experimentally induced muscle disease by combined light, phase and electron-microscopic, as well as histochemical and in selected instances by biochemical and electron-cytochemical methods. An unusually complete collection of biopsy material was accumulated during the past years and collection of case material will be continued. The ultrastructural reaction patterns of organelles and their cytologic significance will be further investigated. A systematic survey of individual muscle diseases will be conducted with the aim of describing, categorizing and classifying ultrastructural changes in the muscle fiber, and when applicable, in the neuromuscular junction, the intramuscular nerves and blood vessels. Whenever possible, the ultrastructural observations will be quantitated by morphometric methods. Rare and hitherto undescribed diseases will be studied intensively by a variety of applicable morphologic, cytochemical and biochemical methods. Experimental studies will be conducted to gain further understanding of ultrastructural mechanisms of muscle fiber degeneration, atrophy and hypertrophy.